2012 Audi Q7 No crank but lights work fine and fan activates

[Shimstar]

Hello all,

I appreciate any help i can get from this forum. I have a Audi Q7 3.0 TDI CRCA engine. I have been rebuilding this as a project car which required drivers wing and core support replacing. The car had always started strong upon the first turn when I purchased it and up until recently. the car has been sat on the drive for about 2 months now while I have been working on it with the little time that I have spare. I had used a trickle charger on 2 occasions using the terminals in the engine bay as I was conscious of the battery going flat. Currently, I am getting no crank at all but all the dash lights etc work fine and does not dim when I turn to crank however after about 5 -10 seconds the radiator fans come on and stay on until I turn the ignition off. I initially assumed it must of been the battery so ordered one from Halfords and installed it but this seemed not to help (I did not register it on a diagnostics). While my old battery was out, I trickle charged it to full and deemed it must not be the battery. I have a Autel which is showing voltages at terminal 15 and 30 around 11.7v ( I am not sure if that is enough to send the signal to the starter motor? I have comms with the ECU so I am hoping it is not the ECU. I am exploring whether it could be a relay because of the trickle charger causing issues etc? I did notice when I was fitting the core support a lot of corrosion around a wire that was connected to the main chassis leg on the right side, and I did use tool to hit off excess rust but left it alone after a pathetic attempt. I also wondered if there was a shock security system that may cause this as when I lowered the car from my jack it did land a little heavy and set the alarm off. I am a bit miffed why it would suddenly not crank. Any ideas or suggestions much appreciated.

[Bigdave1230]

Try putting a jump lead cable from the negative terminal under the bonnet or from the battery negative onto a good metal point direct on the engine and try starting it to rule out a bad earth.

[Stevey Y]

8 hours ago, Shimstar said:

Hello all,

I appreciate any help i can get from this forum. I have a Audi Q7 3.0 TDI CRCA engine. I have been rebuilding this as a project car which required drivers wing and core support replacing. The car had always started strong upon the first turn when I purchased it and up until recently. the car has been sat on the drive for about 2 months now while I have been working on it with the little time that I have spare. I had used a trickle charger on 2 occasions using the terminals in the engine bay as I was conscious of the battery going flat. Currently, I am getting no crank at all but all the dash lights etc work fine and does not dim when I turn to crank however after about 5 -10 seconds the radiator fans come on and stay on until I turn the ignition off. I initially assumed it must of been the battery so ordered one from Halfords and installed it but this seemed not to help (I did not register it on a diagnostics). While my old battery was out, I trickle charged it to full and deemed it must not be the battery. I have a Autel which is showing voltages at terminal 15 and 30 around 11.7v ( I am not sure if that is enough to send the signal to the starter motor? I have comms with the ECU so I am hoping it is not the ECU. I am exploring whether it could be a relay because of the trickle charger causing issues etc? I did notice when I was fitting the core support a lot of corrosion around a wire that was connected to the main chassis leg on the right side, and I did use tool to hit off excess rust but left it alone after a pathetic attempt. I also wondered if there was a shock security system that may cause this as when I lowered the car from my jack it did land a little heavy and set the alarm off. I am a bit miffed why it would suddenly not crank. Any ideas or suggestions much appreciated.

Hi try what Dave suggested and if that won't work its probably an immobiliser issue.

Steve.

[Shimstar]

Thanks for the feedback. I will try this out and see what happens. I have ruled out battery as I purchased two different batteries and tried them out, I have also ruled out relay and fuse issue as I have tested them and also tried 2 new relays that are most likely to be issues. I get  comes with the ecu via my autel mk808bt so most likely not the ecu. 

[Modifyitall]

I am having the same issue with a 2009 Q7 with the 4.2. Performed oil service, vehicle started then stalled. Then no crank. Fans Come on and so do Esp lights. 

Been fidling with relays and various connections. All seems good. It's got a new battery from few months back. 

Anyone have any luck with this past problem on theirs?